Weird Copy rotation constraint behavior
More info is needed, such as is that armature posed(has it been transformed) ?? What are your settings for the C/R constraint ? What axis are you copying ? What are the Bones axis ? Have they got 'roll' compared to the 'owner'?
I can tell by that black dashed line that the bone with the 'Cube' is a child of the last bone in that chain - that means it automatically inherits rotation from its parent (unless it was un-checked). So adding a C/R set to 'World' space, copying all 3 axis should have left it looking just like the bone it was copying. , using 'Local' space on both (Target &amp; Owner) would leave it maybe looking like it is now, depending on the actual rest position. ALWAYS turn on 'axis' display in the 'Armature' display panel, it makes working on stuff much easier to see and understand.